Centrifugal separator with vortex disruption vanes

ABSTRACT

A centrifugal separator for removing particulate contaminants from liquid such as engine lubricants consists of a housing for securing to the engine having a funnel-shaped floor from which oil can drain centrally at a drainage duct. The housing is secured to a legged spider or cage carrying a hollow axle by which the apparatus is secured to the engine and oil delivered to a separation rotor canister. Liquid ejected tangentially from rotor nozzles to cause it to rotate tends to flow around the inside of the housing as a vortex and to prevent rotation of the canister being interfered with by climbing of the vortex or splashing of the liquid from such vortex, one or more vortex disruption vanes are formed with the legs of the cage to deflect liquid.

TECHNICAL FIELD

This invention relates to centrifugal separation apparatus forseparating particulate contaminants from liquids, such as enginelubricants, passed therethrough, and in particular relates to theefficient drainage of low viscosity liquids from such apparatus.

BACKGROUND

Centrifugal separators are well known for use within the lubricationsystems of vehicle internal combustion engines as efficient means forremoving very small particulate contaminants from the constantlyrecirculated liquid lubricant over a long period of operation. Suchcentrifugal separators are usually of the self-powered type, in which aseparation rotor comprising a canister is supported for rotation about arotor axis within a housing, the canister being supplied with liquidlubricant at elevated pressure along the axis and said liquid beingforced from the base of the canister (or other peripheral wall) by wayof substantially tangentially-directed jet reaction nozzles, thereaction to said ejection causing the rotor canister to spin at highspeed about the axis and thereby cause solid particles to migrate fromthe liquid passing through the canister and agglomerate on theperipheral walls thereof. The jet or reaction nozzles are directedsubstantially tangentially with respect to the rotation axis, at leastin a plane orthogonal to the axis, so that jets of liquid which leavethe rotor canister are instantaneously tangential to the fast spinningrotor.

It will be appreciated that the efficiency of separation is dependantupon the rotation speed of the rotor canister and also the quantity oflubricant passed therethrough in a given time, that is in turn,dependant upon the pressure drop between supply (canister) and housingand the dimensions of the nozzles, and within the constraints of suchnozzle dimensions/pressure drops providing sufficient torque to overcomeresistance to commencement of, and continuation of, rotation. Therefore,efficient rotation is dependent upon maintaining a good pressure dropacross the reaction nozzles, that is, with the atmosphere inside thehousing at ambient atmospheric pressure, so that it is necessary todrain this ejected liquid from the housing by gravity. In particular, itis necessary for the liquid to drain from the housing at a rateexceeding that of its supply to the rotor canister so that the ejectedliquid does not accumulate in the housing and rise to a level at whichit contacts, and stalls, the rotor. Such a gravity drainage system isfrequently provided by means of a drainage duct, opening to the floor ofthe housing, of such cross-sectional area that not only can the liquiddrain at a rate in excess of its supply to the rotor, but also cansimultaneously permit venting of the housing to facilitate the drainage.

It will also be appreciated that the rotor canister may also be impededin rotation by droplets of lubricant emitted by the nozzles that splashfrom the surfaces within the housing.

In practice there is almost invariably a requirement for overall minimaldimensions consistent with achieving a desired degree of functionalefficiency, which requirement is met by having the housing dimensionsonly marginally exceeding the rotor, and the housing side wall usuallyconforms to the cylindrical locus of the volume swept by the rotatingrotor, that is, is circular in cross-section that defines said minimalclearance. It will be appreciated that each tangentially directed androtating reaction jet tends to strike the wall at a glancing angle.Whilst this reduces the tendency to splash and impede rotation to someextent, but not completely (and for which reason the axes of thereaction nozzles may be declined towards the floor of the housing), thelubricant is incident on the wall and/or floor at such angle as to causethis liquid to circulate around the housing as it falls towards thefloor thereof and the drain.

It has been found that in some designs the effect of the circulatingliquid in conjunction with a rapidly circulating atmosphere due to therotor creates a vortex effect whereby the liquid accumulates in a vortexcirculating about the periphery of the housing rather than flowingefficiently into the duct, notwithstanding the cross-sectional area ofthe drainage duct, and the level of this spent liquid gradually risesuntil the liquid touches the rotor and causes it to stall. The effect ofsuch stalling is to permit the liquid to cease circulating at speed andbegin to drain property, whereupon the rotor can recommence spinninguntil circumstances again force it to stall. Therefore, it is difficultto know when, and for what percentage of the time, the rotor is actuallyspinning and performing useful centrifugal separation.

The creation of such a vortex in the drainage liquid may be exacerbatedby the structure of the housing in respect of the shape of surfacessurrounding, and leading to, the drainage duct and the axle mount.

Patent specifications GB 2049494 and 2120134 describe a centrifugalseparator in which the floor of a circularly cylindrical housing is inthe form of a substantially conical funnel leading to a central, oraxial, drainage duct. The centrifugal separation rotor comprises acanister mounted for rotation within the housing (from the side wall ofwhich it is separated by only a small radial clearance) on an axle whichis supported, with respect to the housing, raised above the floor by acage or spider comprising an array of divergent legs separatedcircumferentially by drainage apertures for the liquid ejected from therotor.

The above-mentioned GB 2049494 describes briefly the problem of liquidbeing driven up the side wall towards the rotor and suggests attachmentof a small lip on the side wall of the housing as a barrier to this.

It has been found that such centrifugal separator design when used withmodern engines and lubricants, which operate at higher temperatures andlower viscosities, and correspondingly increased throughput for similarpressures, results in a significantly increased tendency for the liquidleaving the rotor nozzles to accumulate within the housing contrary towhat might be expected. The dynamics of such a vortex with liquids ofvarious viscosities suggests that such a lip baffle would produce, forliquids and viscosities typical of that time, a temporary impedance overwhich the vortex would tend to creep, but for liquids of lower operatingviscosities a greater effect in halting the climb of such a vortex, butthis is not experienced in practice.

Viewed somewhat simplistically, a vortex of liquid with a higherviscosity tends to have a more uniform structure and surface on whichthe newly ejected liquid impinges and merges with uniform results,whereas such a vortex of liquid with a low viscosity is found to havelocal turbulence within the body of the vortex and out of its surfaceand a tendency for both the liquid of the vortex and liquid ejected fromthe rotor that is incident on the vortex to splash and froth in theproximity of the rotor to the extent that the presence per se of suchvortex separately from its climbing to fill the gap between rotorcanister and housing, is a source of impedance to canister rotationdetracting from the separation efficiency.

Therefore it is considered that a simple baffle to impede climbing of avortex is not appropriate.

It is an object of the present invention to provide a centrifugalseparator, including a separation rotor that is supported above thehousing floor by a cage, and vortex disruption means to preventaccumulation in the housing of liquid ejected from the rotor as avortex, that is capable of operating more efficiently than hitherto.

According to the present invention a self-powered centrifugal separatorcomprises a housing defined by a cylindrical side wall and by a floorshaped to effect drainage of fluid from the housing into a drainageduct, a centrifugal separation rotor, supported with respect to thehousing for rotation therein about a rotation axis, arranged to receivefluid at elevated pressure and eject it by way of substantiallytangentially directed reaction nozzles into the housing, said rotorbeing supported spaced with respect to the floor of the housing by meansof a cage having a central mounting region coupled to the rotor and asurrounding apertured drainage region extending to the housing, andvortex disruption means, operable to inhibit accumulation of ejectedfluid within the housing, comprising at least one deflection vaneextending over a part of the cage drainage region in the same directionas rotation of the rotor, said vane having a first edge extendingsubstantially parallel to the housing side wall closer than the spacingbetween said side wall and separation rotor and inclined with respect tosaid rotation axis in the direction of rotor rotation, and having asecond edge extending from the end of said first edge to the vicinity ofthe central mounting region.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional elevation through a centrifugal separator inaccordance with the present invention, and

FIG. 2 is a top view of the separator of FIG. 1 with the rotor removed.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a centrifugal separator 10 for use in thelubrication system of a vehicle internal combustion engine comprises ahousing 11 in the form of a right circular cylinder centred on alongitudinal axis 12 and open at one end 13. The housing is surroundedat end 13 by a sealing element 14 for mounting against a surface of thevehicle engine (not shown) which serves to close off the end of thehousing and from which the housing operably depends.

The other end of the housing is formed as a floor 15 which tapers as afunnel to a coaxial drainage duct 16.

An axle 17 extends along the longitudinal axis 12 within the housingfrom a first axle or shaft end region 17′, at which it is secured to amount 20, to a second end region 17″ having a threaded periphery by wayof which the axle, and the separator as a whole, is removably secured tothe vehicle engine.

Referring also to FIG. 2, the mount 20 comprises a cage or spider 21having a central mounting region 22, to which the axle end region 17′ issecured spaced with respect to the floor 15, and a surrounding apertureddrainage region, indicated at 23, extending radially and axially to thehousing. The drainage region of the cage comprises an array of legs 25₁, 25 ₂, 25 ₃ diverging with respect to each other radially outwardlyfrom the central mounting region and separated in a circumferentialdirection by drainage apertures 26 ₁, 26 ₂, 26 ₃, said legs at the endsthereof adjacent the housing being jointed by an annular rim 27 incontact with the housing wall continuously about the periphery. Theannular rim is curled to conform to the corner of the housing betweenthe side wall and floor to align the axes of the axle and housing, andis secured to the housing by welding or the like, whereby the housing issecured with respect to the vehicle by way of the axle 17. That is, theaxle depends from the vehicle and the housing depends from the axle.

The cage is formed from a flat metal sheet by stamping out the drainageapertures 26 ₁ etc and then deforming it axially to provide said centralmounting region, legs and annular rim integrally. The cage appears inelevation with the aperture drainage region as a truncated cone and thelegs and drainage apertures defining a frusto conical plane within thehousing. The legs 25 ₁, etc, of the cage are provided with strength totake axial mounting loads by means of pressed ribs or embossment 28 ₁,28 ₂ 28 ₃.

To further increase the strength of the cage and axle support, acorrespondingly legged bracing member 30, having a central region 31 andintegral legs 32 ₁ etc, is disposed adjacent to the cage sheet with thelegs overlying and joined to each other and the central mounting regions22 and 31 spaced axially as a ‘box section’ into which the end region17′ of the axle is mounted.

The axle 17 contains a passage extending from the end 17″ and opening byway of transverse aperture 35. Upon the axle 17 is supported acentrifugal separation rotor 40 in the form of an annular canisterhaving an integral sidewall and top portion 41 and base portion 42containing an array of jet reaction nozzles, only one of which is shownat 43. The portions 41 and 42 surround a tubular member 44 which extendsfor the length of the rotor and defines an annular enclosure 45 withinthe rotor, the tubular member 44 being apertured at 46 to receive liquidfrom the axle aperture 35 and further carrying at opposite ends thereofbearing bushes 47 and 48 by way of which the rotor is able to undertakehigh speed rotation about the axle.

The jet reaction nozzles 43 et al in the base of the rotor are directedsubstantially tangentially with respect to the longitudinal axis 12 andpossibly slightly declined towards the floor of the housing, sucharrangement being conventional to avoid, as far as is feasible, theliquid from the reaction jets which impinges against the wall of thehousing from splashing against the rotor and disrupting its smoothrotation.

However, the circular cross section of the housing encourages thedischarged liquid to circulate around the housing, low viscosity liquidtending on the one had to swirl more readily and rapidly but on theother hand more turbulently and presenting a rough surface, so thatfrothing and splashing of the vortex liquid itself and subsequentlyejected liquid which is incident upon the liquid of the vortex is morelikely to forth and splash and impinge detrimentally on the rotorcanister. Thus at low liquid viscosities it is perceived as being thepresence per se of a vortex of undrained liquid that is detrimental torotation efficiency, irrespective of the effects of such vortex climbingthe housing wall towards the rotor.

In accordance with the present invention vortex disruption means isprovided, indicated generally at 50 comprising associated with eachradially and axially extending leg of the cage a deflection vane 51 ₁,51 ₂, 51 ₃ respectively which extends from the leg in the same directionas the rotation of the rotor and overlying a part of the cage drainageregion 26 ₁, 26 ₂, 23 ₃ respectively.

Each vane, such as 51 ₁, is formed as an integral extension of a layerof the laminated leg, that is, formed by a sheet of metal, convenientlythat of the leg member 25 ₁. The vane extends in the same direction asrotation of the rotor, overlying the cage drainage region aperature 26 ₁that is, in a generally tangential direction in which it would intersectthe side wall of the housing, but also is bent with respect to the edgeof the leg in a direction towards the wall so that it intrudes into theregion above the drainage region through which the reaction jets areejected such that its lower surface serves to intercept such jets atappropriate rotational positions of the rotor. The ejected liquid whichis incident upon such surface and relatively close to the nozzles fromwhich it issues, is deflected in a generally downward direction towardsthe drainage aperature 26 ₁; by such direction change a reaction boostmay be imparted to the rotor in its direction of spin but mostimportantly the liquid is prevented from contributing to acircumferential vortex flow of such ejected liquid about the side walland rim 27. However, other than when a reaction jet impinge directlyupon the deflection vane, it impinges upon the housing side wall whichdeflects it circumferentially and by gravitational forces, impinge uponany liquid attempting to circulate as a vortex above rim 27. Thedeflection vane extends also to the vicinity of the side wall of thehousing and any part of it effected by the annular rim 27. The vane 51 ₁has a first edge 52 ₁ which extends substantially parallel to, the sidewall being inclined to the longitudinal axis 12 in accordance with thedeflection of the vane; it has a second edge 53 ₁ which extends from theend of the first edge to the vicinity of the rotor mounting region. Thedeflection vane extends from the leg to the extent that the second edgeextends (in plan view) in a substantially radial direction towards thehousing wall.

The intersection between side wall and rim 27 is both cranked, inrespect of the side wall locating the rim and the additional thicknessof the rim, and curved by the curled form of the rim. Therefore it isconvenient to cut the edge of the vane blank before bending so that itconforms closely to the shape locally. The first edge 52 ₁, isconveniently straight, notwithstanding that it is intended to lieagainst a side wall curved in the circumferential direction, providingthat any part of the edge is closer to the side wall than the separationbetween rotor canister and side wall. Preferably the first edge isarranged to contact the wall at one or both edges, but contact is notessential if the maximum spacing is not exceeded, permitting the vane tobe set with assembly of the cage prior to disposal within the housing.

Whereas the vane does not require securing to the housing, insofar asthe cage rim 27 is (or may be) secured by spot welding to the housingthe first edge of the vane may also be secured directly to the housing.The above description relating to vane 25 ₁, is of course applicable tothe other vanes 25 ₂ and 25 ₃.

Each vane is conveniently a flat plane so that liquid ejected from therotor canister in a tangential direction is deflected inwardlyperpendicularly to the legs/drainage apertures whilst being a simplestructure to manufacture, but if desired the vane may have a curvaturealong and/or across all or part of it to modify the redirection of theliquid or disruption of any vortex tending to form.

In the form illustrated, each vane overlies the respective drainageaperture, to an extent which does not interfere with the effective areaas seen by liquid above it, by bending the vane upwardly towards therotor and housing. It will be appreciated that if desired the vane maybe less inclined, if at all, and extend further in a circumferentialdirection until intersection with the side wall, that is, tangentially.

It will be appreciated that although it is convenient to have aplurality of substantially identical deflection vanes extending one fromeach of the cage legs, they may differ in dimensions and/or inclination,absolutely and with respect to each other, and fewer vanes may beemployed. For example, a single vane only may be employed, its presenceserving to impede the formation of any rotational liquid and deflect ittowards the floor.

It will be appreciated that each deflection vane may be formedintegrally with either layer of such laminated leg structure or evenformed non-integrally, being either secured to any such leg structureor, in the case of such laminated leg structure, being sandwichedbetween laminations. Any deflection vane may be formed of other than theabove-mentioned sheet metal, provided it is compatible with theoperating conditions encountered within the housing.

It will be appreciated that the axle mount cage may be formedsubstantially as described but omitting the bracing member, whichstructural form limits only the options available for mounting thedeflection vanes.

It will be appreciated that such an axle mount cage may be formed withother than discrete identifiable legs separated by arcuate drainageapertures, for example, as a mesh or perforated sheet structure, but byappropriate construction one or more such deflection vanes may beemployed attached to such mount or separately mounted within the housingbetween the mount and rotor.

The centrifugal separator structure described above has a fixed axlewhich supports and defines a rotation axis for the separation rotorcanister. It will be appreciated that the present invention isapplicable without change where the separation rotor is of the type thathas an integral rotatable spindle which is mounted in place of the axle.

Similarly, the floor of the housing need not be of the funnel shape ofthe above-described embodiment, as such effects occur with substantially‘flat’ floors where such rotational motion is permitted to build up inthe ejected fluid.

What is claimed is:
 1. A self-powered centrifugal separator comprising ahousing defined by a cylindrical side wall and by a floor shaped toeffect drainage of fluid from the housing into a drainage duct, acentrifugal separation rotor, supported with respect to the housing forrotation therein in a predetermined direction about a rotation axis, andarranged to receive fluid at elevated pressure, and to eject the fluidby way of substantially tangentially directed reaction nozzles into thehousing, said rotor being supported spaced with respect to the floor ofthe housing by means of a cage having a central mounting region coupledto the rotor and a surrounding apertured drainage region extending tothe housing, and vortex disruption means, operable to inhibitaccumulation of ejected fluid within the housing, comprising at leastone deflection vane overlying a part of said drainage region in saidpredetermined direction of rotation of the rotor, said vane having afirst edge thereof extending substantially parallel to the cylindricalside wall closer than the spacing between said cylindrical side wall andseparation rotor and inclined with respect to said rotation axis in saiddirection of rotor rotation, and having a second edge extending from anend of said first edge to a location proximate the central mountingregion.
 2. A centrifugal separator as claimed in claim 1 wherein saidsecond edge of the vane is arranged to extend substantially radiallywith respect to the housing.
 3. A centrifugal separator as claimed inclaim 1 wherein at least one said vane is substantially planar.
 4. Acentrifugal separator as claimed in claim 1 wherein said first edge isstraight and is arranged to touch the side wall at at least one end ofsaid edge.
 5. A centrifugal separator as claimed in claim 1 wherein theapertured drainage region of the cage comprises an array of legsextending substantially radially outwardly from the central mountingregion to the housing and separated in a circumferential direction bydrainage apertures.
 6. A centrifugal separator as claimed in claim 5wherein said legs at the end thereof adjacent the housing are joined byan annular rim in contact with the cylindrical wall continuously aboutthe periphery.
 7. A centrifugal separator as claimed in claim 6 whereinthe rim is curved to conform to the junction between the cylindricalside wall and floor and the vane is shaped to conform with a curvatureof the rim.
 8. A centrifugal separator as claimed in claim 6 wherein atleast one of said legs and annular rim are secured to the housing at thejunction between the side wall and floor of the housing.
 9. Acentrifugal separator as claimed in claim 8 wherein said at least onedeflection vane comprises a plurality of deflection vanes, and furtherwherein at least one of said legs has one of said plurality ofdeflection vanes extending integrally therefrom.
 10. A centrifugalseparator as claimed in claim 5 wherein said at least one deflectionvane comprises a plurality of deflection vanes, and further wherein atleast one of said legs has one of said plurality of deflection vanesextending integrally therefrom.
 11. A centrifugal separator as claimedin claim 5 wherein the cage is formed of pressed sheet metal thatincludes the central mounting region integrally with the legs and acorrespondingly legged bracing member disposed with the correspondinglegs overlying and joined to each other, each deflection vane of thevortex disruption means being formed integrally with a leg of thebracing member.
 12. A centrifugal separator as claimed in claim 11wherein the bracing member does not extend radially to the housing. 13.A centrifugal separator as claimed in claim 5 wherein the cage is formedof pressed sheet metal that includes the central mounting regionintegrally with the legs and a correspondingly legged bracing memberdisposed with the corresponding legs overlying and joined to each other,each deflection vane of the vortex disruption means being secured withrespect to the legs of the cage by sandwiching between said cage andbracing member.
 14. A centrifugal separator as claimed in claim 13wherein the bracing member does not extend radially to the housing.